Question : Problem: Unknown Device USB\Root_hub20\

We are having an issue with a new Lenovo Thinkcentre PC where in the device manager it is listing an Unknown device.  The Device ID is USB\root_hub20\ so I assume that it is the root hub for the USB enhanced controller.  I have already downloaded the Chipset inf and reinstalled that also forcing the controller to pull the updated driver, however nothing I do will assist in finding the appropriate driver for the 2.0 root hub.
  We have removed all the USB devices except the mouse and rebooted, uninstalled the unknown, reinstalled the unknown and I am about at my wits end with the thing.

Any suggestions on how I can get this device functioning?

Answer : Problem: Unknown Device USB\Root_hub20\

are the usb ports functional?  if not, you cannot fix it with a driver install.
you can check the usb funcionality by running from a knoppix cd - it supports usb :
ftp://ftp.uni-kl.de/pub/linux/knoppix/KNOPPIX_V5.1.0CD-2006-12-30-EN.iso